TEHRAN, Iran — Protesters battled police over Iran's disputed election and shouted their opposition from the rooftops Sunday, but President Mahmoud Ahmadinejad dismissed the unrest as little more than "passions after a soccer match" and drew his own huge rally of support.

Just after sundown, cries of "death to the dictator" echoed through Tehran as thousands of backers for Ahmadinejad's rival, Mir Hossein Mousavi, heeded a call to bellow from the roofs and balconies. The deeply symbolic act recalled the shouts of "Allahu Akbar," or God is Great, to show opposition to the Western-backed monarchy before the 1979 Islamic Revolution.

The scenes summed up the showdown over the disputed elections: an outwardly confident Ahmadinejad exerted control, while Mousavi showed no sign of backing down and could be staking out a new role as powerful opposition voice.

Mousav's supporters plan a rally in Tehran on Monday to protest against the election results.

His charges that Friday's vote was riddled by fraud brought sympathetic statements from Vice President Joe Biden and other leaders. Mousavi made a direct appeal with Iran's ruling clerics to annul the result, but the chances were considered remote.

With his wide network of young and middle-class backers, Mousavi could emerge as a leader for Iran's liberal ranks and bring internal pressure on Ahmadinejad and Iran's theocracy to take less confrontational policies toward the West.

Some of the worst unrest in a decade
But the struggle Sunday was on the streets in the worst unrest in Tehran since student-led protests 10 years ago.

Demonstrators were back on the streets with the same tactics: torching bank facades and trash bins, smashing store windows and hurling rocks at anti-riots squads in Tehran. Police responded with baton-wielding sweeps — sometimes targeting bystanders — and the regime shut down text messaging systems and pro-reform Internet sites.

There was no official word on casualties.

Authorities detained top Mousavi aides, including the head of his Web campaign, but many were released Sunday after being held overnight.

Iran's deputy police chief, Ahmad Reza Radan, told the official Islamic Republic News Agency that about 170 people have been arrested. It was not known how many remained in custody.

Mousavi has urged his supporters to channel their anger into peaceful acts of dissent. But the official clampdown on the Internet links blunted the reach of the message. At the same time, Mousavi went to the pinnacle of power to try to reverse the election decision.

In a letter to the Guardian Council — a powerful 12-member clerical body closely allied to Supreme Leader Ayatollah Ali Khamenei — he claimed "fraud is evident."

The letter, posted on Mousavi's Web site that is accessible outside Iran, didn't specify his allegations but claimed that his envoys were unfairly blocked from monitoring polling stations. Iran does not allow outside or independent election observers. The Guardian Council must certify all election counts.

'No legal credibility'Mousavi later met Khamenei — who has almost limitless power — to press his appeal, said Shahab Tabatabaei, a prominent activist in Mousavi's pro-reform camp.

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It was likely a long-shot mission by Mousavi, 67, who served as prime minister in the 1980s. Khamenei has already given his blessing to the election outcome and it would be extraordinary for him to publicly change his position.

In a news conference, Ahmadinejad called the level of violence "not important from my point of view" and likened it to the intensity after a soccer game.

"Some believed they would win, and then they got angry," he said. "It has no legal credibility. It is like the passions after a soccer match. ... The margin between my votes and the others is too much and no one can question it."

"In Iran, the election was a real and free one," he told a room packed with Iranian and foreign media.

But Ahmadinejad also accused international media of launching a "psychological war" against the country.

Some journalists asked to leave
Iranian authorities have asked some foreign journalists who were in Iran to cover the elections to prepare to leave. Nabil Khatib, executive news editor for Dubai-based news network Al Arabiya, said the station's correspondent in Tehran was given a verbal order Sunday from Iranian authorities that the office will be closed for one week.

No reason was given for the order, but the station was warned several times Saturday that they need to be careful in reporting "chaos" accurately.

A sustained and growing backlash to Iran's power could complicate the country's policies at a pivotal time.

President Barack Obama has offered to open dialogue after a nearly 30-year diplomatic freeze. Iran also is under growing pressure to make concessions on its nuclear program or face possible more international sanctions.

On NBC television's "Meet the Press," Biden said: "Is this the result of the Iranian people's wishes? The hope is that the Iranian people, all their votes have been counted, they've been counted fairly. But look, we just don't know enough" since Friday's vote.

In Paris, French Foreign Minister Bernard Kouchner said his country is "very worried" about the situation in Iran and criticized the "somewhat brutal reaction" to the election protests.

By mid-afternoon, tens of thousands of Ahmadinejad supporters filled Vali Asr Street — the same place a massive pre-election rally was held by Mousavi last week. Ahmadinejad's forces waved Iranian flags and green Islamic banners, an obvious response to Mousavi's campaign that adopted green as its trademark color.

Ahmadinejad even donned a green scarf and noted its traditional Islamic references as the favored color of Prophet Mohammad.

"Ahmadinejad is a hero," said a 34-year-old supporter Mohammad Chegini. "He cares for the poor. He is brave and stands up to the West. It is Ahmadinejad who made uranium enrichment a reality in this country."

Using Web chat lines, phone calls and word of mouth, the message was passed for Mousavi's backers to shout "death to the dictator" and "Allahu Akbar." The historical connection of the act was hugely significant for Iranians. It was how the leader of the Islamic Revolution, the late Ayatollah Ruhollah Khomeini, asked the country to unite in protest against the monarchy and was used later to mark its anniversary.

In one neighborhood, anti-riot police tried to disperse people joining in the cries from a street corner, but the crowds threw rocks at the officers and they withdrew.

Mousavi's newspaper, Kalemeh Sabz, or the Green Word, did not appear on newsstands Sunday. An editor, who spoke on condition of anonymity because of the sensitivity of the situation, said the paper never left the printing house because authorities were upset with Mousavi's statements.

The paper's Web site reported that more than 10 million votes in Friday's election were missing national identification numbers similar to U.S. Social Security numbers, which make the votes "untraceable." It did not say how it knew that information.

"Don't worry about freedom in Iran," Ahmadinejad said at the news conference after a question about the disputed election. "Newspapers come and go and reappear. Don't worry about it."